Gulf of Maine Seasonal Sea Surface Temperature Update

Seasonal Patterns in Sea Surface Temperatures

Author

Adam Kemberling

Published

March 20, 2024

Winter 2024 Highlights

For this seasonal report we present an analysis of SST for winter (December 1, 2023 - February 28, 2024).

Winter is an important time of year for the Gulf of Maine. During this time of year sea surface temperatures are typically falling, and the surface stratification breaks down. The breakdown of stratification allows for vertical mixing in the water column, which helps transport important nutrients through the near-surface waters. These nutrients are what fuel the spring phytoplankton blooms that support the high productivity in the region. Vertical mixing may be enhanced in Winter with the help of Nor’Easters, which are most common this time of year and stir up the water column with rough seas and strong winds.

This year, the average SST for the Gulf of Maine was 43.35°F, making it the 23rd hottest winter on record for the period of 1982-2023 — the period over which the satellite data used are available.

This seasonal average temperature is -0.71°F above the 1991–2020 climatological reference period (CRP) winter average of 44.06°F.

Weekly Temperatures

Table 1 highlights how the SST for each week this winter compares to the 1991-2020 CRP for the area shown in Figure 8. The observed SST, long-term average SST, and SST anomalies (i.e., departures from the long-term average SST) are shown.

winter average SST was on average -0.71°F or more above normal during the fall, with weekly averaged SST anomalies ranging from -1.7°F to +0.4°F.

Table 1:

Average weekly sea surface temperatures in the Gulf of Maine

Table 1. Weekly Average Sea Surface Temperatures - Winter
(December 1, 2023 - February 28, 2024)
One-Week Period Observed Temperature Climatological Average Temperature Anomaly

Dec 01 - Dec 02

49.3°F (9.6°C)

49.4°F (9.7°C)

-0.1°F (-0.1°C)

Dec 03 - Dec 09

48.3°F (9.1°C)

48.8°F (9.3°C)

-0.4°F (-0.2°C)

Dec 10 - Dec 16

47.4°F (8.5°C)

47.8°F (8.8°C)

-0.5°F (-0.3°C)

Dec 17 - Dec 23

46.7°F (8.2°C)

46.9°F (8.3°C)

-0.2°F (-0.1°C)

Dec 24 - Dec 30

46.4°F (8.0°C)

45.9°F (7.8°C)

0.4°F (0.2°C)

Dec 31 - Jan 06

45.0°F (7.2°C)

45.1°F (7.2°C)

-0.0°F (-0.0°C)

Jan 07 - Jan 13

43.8°F (6.6°C)

44.2°F (6.8°C)

-0.4°F (-0.2°C)

Jan 14 - Jan 20

42.1°F (5.6°C)

43.4°F (6.3°C)

-1.2°F (-0.7°C)

Jan 21 - Jan 27

40.9°F (5.0°C)

42.6°F (5.9°C)

-1.7°F (-0.9°C)

Jan 28 - Feb 03

40.9°F (4.9°C)

42.0°F (5.5°C)

-1.1°F (-0.6°C)

Feb 04 - Feb 10

40.4°F (4.7°C)

41.4°F (5.2°C)

-1.0°F (-0.6°C)

Feb 11 - Feb 17

40.0°F (4.5°C)

40.9°F (4.9°C)

-0.9°F (-0.5°C)

Feb 18 - Feb 24

39.2°F (4.0°C)

40.5°F (4.7°C)

-1.3°F (-0.7°C)

Feb 25 - Feb 28

38.8°F (3.8°C)

40.2°F (4.6°C)

-1.5°F (-0.8°C)

Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatological Reference Period: 1991-2020.

Monthly Statistics

Table 2 shows monthly average SST for winter 2024; each month was within -1°F or more above the 1991-2020 CRP.

February showed the largest deviation from the long-term climatological average, with an average SST anomaly of -1.08 °F, making it the 34th warmest February` on record.

December and January were warmer at -0.1 & 0.9°F below the long-term average—coming in as the 19th and 25th warmest December and January on record, respectively.

Table 2:

Average monthly sea surface temperatures in the Gulf of Maine

Table 2. Monthly Average Sea Surface Temperatures - Winter
(December 1, 2023 - February 28, 2024)
Month Rank (1982-2023) Observed Temperature Climatological Average Temperature Anomaly

December

19

47.3°F (8.5°C)

47.4°F (8.6°C)

-0.1°F (-0.1°C)

January

25

42.6°F (5.9°C)

43.5°F (6.4°C)

-0.9°F (-0.5°C)

February

34

39.8°F (4.3°C)

40.9°F (5.0°C)

-1.1°F (-0.6°C)

Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatological Reference Period: 1991-2020.

How Does this Winter Compare to the Past?

2024 was the 23rd warmest winter season observed in the Gulf of Maine during the 41 years we have satellite data to analyze, a departure winter seasons in recent years, which experienced well-above average SSTs.

Figure 1: A ranking of the 25 warmest winter seasons for the Gulf of Maine in the satellite record (1982-2023). 2023-24 was the twenty-third warmest winter on record.

Marine Heatwave Conditions

The most commonly used definition of a “marine heatwave” (MHW) is when daily average SSTs exceeded the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event. Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 0% of days this winter.

Figure 3: A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from December 1, 2023 through February 28, 2024. Black lines represent the long-term (i.e., 1991 – 2020) average SST, the 10th percentile, and 90th percentile for a given day in the Gulf of Maine; a solid line (red for marine heatwave or blue for a non-event) indicate the observed SST this year; red (above 90th percentile) and blue (below 90th percentile) shading illustrates how far the observed SST is from the climatological average.

Presenting SST conditions in terms of anomalies ( Figure 4 ) as opposed to absolute values ( Figure 3 ) illustrates in greater detail the magnitude of MHW conditions throughout the winter.

The highest daily SST anomalies for winter 2023-2024 occurred towards the end of December, with anomalies near 0°F above the climatological average. All daily SSTs after January 1st were below the climatological average, contributing to this season’s unexpectedly low ranking.

Figure 4: A timeseries of daily average SST anomalies in the Gulf of Maine (solid colored line) compared to the long-term climatological mean, 10th, and 90th percentiles (solid black lines) in the Gulf of Maine for the period December 1, 2023 through February 28, 2024.

Heatmap of Temperature Anomalies and Heatwave Events

Looking at the full record of daily SST anomalies in the Gulf of Maine (Figure 5), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.

Winter SSTs in the previous 3 years had been noteworthy for their extended MHW conditions, part of the long-term trend of unseasonably warm fall since 2012 (Figure 2). The relatively cold winter in the Gulf of Maine this year were an extension of cooler fall conditions, but stand out against above-average winter conditions since 2012.

Figure 5: Heat map of daily SST anomalies from the beginning of 1982 through March 2024. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency, duration, and intensity of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Spatial Distribution of Seasonal Anomalies

From an aerial perspective, the Gulf of Maine experienced below-average SSTs during winter of 2024. In general, conditions were cooler in the deeper-water basins and warmer in shallow protected areas like the Bay of Fundy and Massachusetts Bay. The highest seasonally averaged SST anomaly in the Gulf of Maine was 2.29°F - located near the Bay of Fundy.

Figure 6: Map of average SST anomalies for each grid cell in the satellite record for spring 2023. The box outlined by the black dashed line denotes the region of study for the analysis (see Figure 8). Darker red regions indicate warmer anomalies. Black contours have been added at 100m and 200m depth

Monthly Temperature Anomalies

Average monthly SST anomalies are shown in Figure 7.

Figure 7: This series of maps shows the average monthly SST anomaly for December 2023, January 2024, and February 2024. The box outlined by the black dashed line denotes the region of study for the analysis. Darker red regions indicate warmer anomalies.

About the Updates:

Over the past decade, scientists have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To help keep you informed, we share seasonal and annual updates about conditions in the Gulf of Maine.

Read on for an inside look at what we’ve learned in our winter 2023 Gulf of Maine warming update.

The Gulf of Maine Region

For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (Figure 8), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is displayed below. This area is consistent with previous seasonal and annual reports that scientists at GMRI have produced.

An overhead view of the Gulf of Maine region. Landmasses and political boundaries for the United States and Canada are displayed. A blue dotted line outlining a box with a transparent blue fill is shown to demark where satellite data for the analysis has been used.

Figure 8: Spatial domain used for Gulf of Maine SST analyses. Depth contours are colored at 100 m intervals up to 600 m; deeper blues indicate deeper water depths

Data Sources:

NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.

Citing This Work

If you would like to cite this report, please use:

Gulf of Maine Research Institute. 2024. Gulf of Maine Warming Update: Winter 2024

Note About the Data:

The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.

Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.

 

A work by Adam A. Kemberling

Akemberling@gmri.org